Precise monitoring of the blood glucose level is a vital precaution for a large number of patients suffering from diabetes, since these patients may also be obliged to undergo other treatments for other health problems at the same time.
Numerous miniaturized apparatus already exist for measuring the glucose level, which determines the quantity of insulin to be administered, and to make the everyday life of such patients easier. These apparatus generally rely upon an electrochemical measurement by amperometrics, in the presence of a specific enzyme in glucose, with the blood sample being deposited on a disposable sensor.
The enzyme that is currently most used is glucose oxydase (GOD) because it is very specific to glucose, to the exclusion of all other oligosaccharides, and because it is insensitive to temperature variations as regards the signal height. Glucose oxydase has, however, the drawback of being very sensitive to the presence of oxygen, whose concentration may be variable, which distorts the precise glucose level measurement. In order to reduce or eliminate this drawback, it has been proposed to use a mediator, which will accelerate the electron transfer and make the influence of oxygen negligible. From among the most used mediators, we may cite ferrocene and its derivatives, and osmium complexes, such as those disclosed in U.S. Pat. No. 5,393,903.
One could also use glucose dehydrogenase (GDH), which has the advantage of being insensitive to the presence of oxygen. Glucose dehydrogenase has, however, the drawback of being less glucose specific and of interfering with other saccharides, oligosaccharides, and oligopolysaccharides, such as maltose, which results in the glucose level being overestimated and thus to insulin being inappropriately administered. This constitutes a serious drawback for diabetic patients, who must also, for example, undergo continuous ambulatory peritoneal dialysis (CAPD) by absorbing icodextrine, which is hydrolysed by α-amylase with oligosaccharides such as maltose, maltotriose or maltotetraose.